const fs=require('fs');
fs.writeFile('./bbb.text','hello world',{
    encoding:'utf-8',
    flag:'a+'
},(err)=>{
    console.log('写入文件结果：',err);
});
const writeStream=fs.createWriteStream('./ccc.txt',
{flags:'a'});
writeStream.on('open',(fd)=>{
    console.log('通过流将文件打开',fd);
});
writeStream.write('coderwhy');
writeStream.write('aaaa');
writeStream.write('bbbb',(err)=>{
    console.log('写入完成：',err);
});
writeStream.on('finish',()=>{
    console.log('写入完成了');
});
writeStream.on('close',()=>{
    console.log('文件被关闭');
});
writeStream.end('哈哈哈哈');